// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// MSVC++ requires this to be set before any other includes to get M_PI.
#define _USE_MATH_DEFINES
#include <cmath>
#include <sstream>

#include "media/base/audio_hash.h"

#include "base/macros.h"
#include "base/strings/stringprintf.h"
#include "media/base/audio_bus.h"

namespace media {

AudioHash::AudioHash()
    : audio_hash_()
    , sample_count_(0)
{
}

AudioHash::~AudioHash() { }

void AudioHash::Update(const AudioBus* audio_bus, int frames)
{
    // Use uint32_t to ensure overflow is a defined operation.
    for (uint32_t ch = 0; ch < static_cast<uint32_t>(audio_bus->channels());
         ++ch) {
        const float* channel = audio_bus->channel(ch);
        for (uint32_t i = 0; i < static_cast<uint32_t>(frames); ++i) {
            const uint32_t kSampleIndex = sample_count_ + i;
            const uint32_t kHashIndex = (kSampleIndex * (ch + 1)) % arraysize(audio_hash_);

            // Mix in a sine wave with the result so we ensure that sequences of empty
            // buffers don't result in an empty hash.
            if (ch == 0) {
                audio_hash_[kHashIndex] += channel[i] + sin(2.0 * M_PI * M_PI * kSampleIndex);
            } else {
                audio_hash_[kHashIndex] += channel[i];
            }
        }
    }

    sample_count_ += static_cast<uint32_t>(frames);
}

std::string AudioHash::ToString() const
{
    std::string result;
    for (size_t i = 0; i < arraysize(audio_hash_); ++i)
        result += base::StringPrintf("%.2f,", audio_hash_[i]);
    return result;
}

bool AudioHash::IsEquivalent(const std::string& other, double tolerance) const
{
    float other_hash;
    char comma;

    std::stringstream is(other);
    for (size_t i = 0; i < arraysize(audio_hash_); ++i) {
        is >> other_hash >> comma;
        if (fabs(audio_hash_[i] - other_hash) > tolerance)
            return false;
    }
    return true;
}

} // namespace media
